MADRID, Spain — Dozens of wildfires raged across northwestern Spain on Monday, and authorities said most of the blazes that have killed three people and destroyed thousands of acres of woodland were deliberately set.

More than 90 wildfires were reported over the weekend in Galicia, where almost 12,355 acres has been charred. Authorities said 85 were still ablaze Monday.

Many of the fires had been started near each other with a clear intention that winds would fan them into one big conflagration, said fire department spokeswoman Iria Mendez.

Most were started on wooded slopes near inhabited areas, regional environment spokesman Alfredo Suarez Canal said.

Police arrested a 24-year-old man suspected of starting several wildfires after authorities acted on tips from residents in Cerdedo, a town in Pontevedra, the Galician regional government said.

The man, whom authorities have not linked to any of the three fire-related deaths in Galicia since Thursday, was identified only by his initials.

Earlier, authorities said a 74-year-old man had died while fighting a fire in Pontevedra. Manuel Aprada Fontella, who had joined other neighbors as a volunteer in the firefighting operation, was found late Sunday.

Wildfires also were reported on the other side of Spain in the northeastern region of Catalonia.

More vigilanceForest fires in Spain and other Mediterranean countries char hundreds of thousands of acres of land every year. Spain’s national and regional governments agreed to step up vigilance after 17 people died in fires last summer.

The Environment Ministry has been trying to reduce the number of forest fires that affect Spain each year.

The number of fires that have burned more than 2.5 acres has dropped from more than 6,200 in 2005 to fewer than 3,000 in 2006 for the January-July period, according to ministry figures. Fires charred 88,635 acres, down from 233,370 acres in 2005, the ministry added.

Authorities attribute the drop to preventive measures, including banning barbecues in the countryside in dry regions, and more effective campaigns to clear roadside garbage and forests of fallen leaves and branches.